The present invention relates to an apparatus for recording and/or reproducing information by reciprocating a card-like or sheet like information bearing medium relative to a head which records and/or reproduces information. In the present invention, the term information recording and reproducing apparatus means any of the record-only apparatus, reproduce-only apparatus and record/reproduce apparatus.
The prior art apparatus for recording and reproducing information by using a light beam uses an optical disk which is a rotating disk-shaped recording medium, an optical card which is a reciprocating card-shaped reading medium or an optical tape. Such apparatus have their respective features and are selectively used depending on applications and purposes. Among others, the optical card has a wide range of applications because of easiness of manufacture, portability and high accessability.
There are many ways to scan the light beam on the optical card. In one method, an irradiation position of the light beam is linearly and relatively moved on the recording medium to attain the reciprocal movement, and the beam irradiation position is relatively moved orthogonally to the direction of the reciprocal movement to attain the scan operation. In this method, the mechanism is simple, the precision is high and the effective space on the medium is large.
There are many mechanisms for reciprocating the card-like medium. A mechanism shown in FIG. 1 is frequently used for a magnetic card.
In FIG. 1, numeral 1 denotes a magnetic card, numeral 2 denotes a magnetic stripe which is an information recording area, numeral 3 denotes a magnetic head, and numerals 4a-4d denote roller pairs at least one of each of which has a driving power. The magnetic card 1 pinched by the roller pairs 4a-4d is reciprocally moved in a direction A as the rollers 4a-4d are rotated. Through this movement, a processing area on the magnetic stripe 2 is moved under the magnetic head 3 so that the information on the processing area is reproduced or new information recorded on the processing area.
Where the information width in the direction B shown in FIG. 1 is wide like in the magnetic card or an optical card which uses a bar code, the mechanism shown in FIG. 1 is acceptable, because even if the card 1 is skewed to the direction B by the misalignment during the insertion or during the reciprocal movement by the rollers 4a-4d, it does not affect to the recording and reproducing since the information width in the direction B is sufficiently wide. In the magnetic card and bar code optical card, the information is recorded or reproduced in one reciprocation of the card 1. Accordingly, the card feed speed need not be so high.
With the advancement of the light recording technique, it has been proposed to reduce a size of an information unit (called pit) to 5 .mu.m-10 .mu.m and increased information quantity stored in one card 1 to 10-20 Mbits. Where such a large quantity of information is reproduced and recorded, a high recording and reproducing speed is required as a matter of course. It is needless to say that the mechanism shown in FIG. 1 is not proper for such optical card, because the skew in the direction B is critical. The variation of the speed in the direction A and the durability of the card 1 are also critical because the card 1 is reciprocated at a high speed in the direction A.
As an approach to solve the above problem, a construction is proposed in which the card 1 is mounted on a card mount which in turn is reciprocated (U.S. Ser. No. 814,774, the same assignee). An example of such card mount is shown in FIGS. 2 and 3.
In FIG. 2, numeral 11 denotes a card mount (called a shuttle) and numerals 12 and 12' denote projections provided at one end of the shuttle 11. The projections 12 and 12' have coaxial apertures into which bearings 14 and 14' made of high sliding shaft 13 is fitted to the bearings 14 and 14'. Rollers 15 and 16 are rotatably mounted at the other and of the shuttle 11 and a fixed shaft 17 is pinched by the rollers 15 and 16. The shuttle 11 is slidably mounted to the fixed shafts 13 and 17. Play between the fixed shaft 13 and the bearings 14 and 14', and play between the fixed shaft 17 and the rollers 15 and 16 are small, just so long as the shuttle 11 can be smoothly slid.
The shuttle 11 has a step 18 to form a gap which is slightly wider than a thickness of a card 21, between card pushing members 19 and 20. Numerals 22 and 22' denote resilient members which urge the card 21 to an edge 18' of the step 18. Numeral 23 denotes a projection provided on the shuttle 11. When the card 21 is inserted from a left bottom position in FIG. 2, the projection 23 serves to stop the card 21 at a predetermined position. Numeral 24 denotes a belt having a portion thereof fixed to the shuttle 11.
Numeral 25 denotes an information recording area on the card 21, numeral 26 denotes an information track, numeral 27 denotes an optical head and numeral 28 denotes a light beam for recording and reproducing information. In FIG. 3, numeral 29 denotes a rotatable pulley, and numeral 30 denotes a pulley mounted on a servo motor 31. The belt 24 is wound on the pulleys 29 and 30, as the servo motor 31 rotates, the shuttle 11 is reciprocated to left and right in FIG. 3 The optical head 27 is movable, by a mechanism not shown, in a direction orthogonal to the reciprocation direction of the shuttle 11. Thus, the light beam 28 can be positioned to any position in the recording area 25.
A light information recording and reproducing apparatus which uses the above mechanism is disclosed in U.S. Ser. No. 814,774 mentioned above.
It is not so difficult to keep the play between the fixed shaft 13 and the bearings 14 and 14' and the play between the fixed shaft 17 and the rollers 15 and 16 within approximately 5 .mu.m. It is not so difficult to keep the variation of the card thickness within approximately 0.1 mm. Accordingly, the gap between the step 18 and the card retainer 19 and 20 is within 0.1 mm in the worst case. In this case, it is practical to record and reproduce the information by auto-tracking and auto-focusing servo controls to pits of 5-10 .mu.m diameter. Further, reciprocation movement at a speed of several reciprocations per second can be attained.
In such light information recording and reproducing apparatus which uses the optical card, it is desirable that the number of information pits recorded or reproduced in a unit time period is large, that is, a transfer rate is high. However, in order to increase the transfer rate, it is necessary to increase the reciprocation speed of the shuttle 11. On the other hand, it is desirable that the shuttle speed is constant during recording or reproducing of information because, if the speed varies, the size of the recording pit varies even if the light beam 28 is turned on and off at a constant frequency, and complex processing is required to resolve the size irregularity problem.
The shuttle 11 has a certain mass even if it is made of a light material such as plastic. Therefore, a speed rise-up time is required before the shuttle speed reaches a predetermined speed after reversal, and a speed fall-down time is required before the shuttle is stopped from the constant speed.
An example of such speed control is shown in FIG. 4, in which an ordinate represents a velocity v of the shuttle 11 and an abscissa represents a time t. Numeral 32 denotes a rise-up area in which the velocity rises up from a stop condition, numeral 33 denotes a constant speed area, numeral 34 denotes a decelaration area in which the speed is decelerated to zero, numeral 32' denotes an acceleration area in the opposite direction after reversal, numeral 33' denotes a constant speed area in the opposite direction and numeral 34' denotes a deceleration area in which the speed is decelerated to zero. This operation is repeated. Such speed control may be attained by a method disclosed in U.S. Ser. No. 814,774 filed by the present applicant.
In the speed control shown in FIG. 4, it is desirable that gradients of the areas 32, 32' 34 and 34' are sharp, because wasted time not used for recording or reproducing is reduced and the transfer rate is increased, and the distance across which the shuttle 11 is moved in the rise-up time and the fall-down time is small and hence a compact apparatus is attained. However, since the shuttle 11 has the mass as described above, if the gradients of the areas 32, 32', 34 and 34' are to be sharp, a high torque output is required for the motor 31 and power consumption increases. As a result, the size of the power supply mounted on the apparatus increases.